The present invention relates to a plant for continuous flow freezing of items such as edible ice products, which are introduced while in/on a conveyor, namely a tray conveyor of the kind which comprises a conveyor chain with trays or plates supporting the individual items to be frozen extending transversely from the chain, and where the conveyor chain in vertical upwards or downwards direction or in a spiral-like manner, preferably with a plurality of windings hereof in the freezing section of the freezing plant, is guided sideways by driving elements and/or guiding or driving chain wheels engaging with the chain, and is led up and/or down in the freezer from an inlet to an outlet from the freezing section, and where the freezing temperature in the freezing section is provided by means of freezing air circulating in the freezing section, and which is brought about by means of at least one freezing aggregate and at least one associated freezing-air circulation blower or fan maintaining a flow of freezing air which passes around and across the items to be frozen which are transported on the conveyor chain trays. Regardless of its type, in the following, the conveyor will be referred to as a tray conveyor.
A known plant of this kind is described in U.S. Pat. publication No. 5,520,013. In this plant, the chain conveyor is led into the freezing section with several items lying on each tray, and is driven vertically up and down over a central support frame, where on opposite sides of this frame there is arranged a freezing aggregate on the one side and a freezing-air circulation blower on the other side in relation to the frame. According to this USA patent publication, two sets of such aggregate arrangements can exist one above the other, i.e. partly with a first freezing aggregate arranged over the blower belonging to the second of the two freezing aggregates, and partly with the blower belonging to the first freezing aggregate arranged over the second of the two freezing aggregates. Two circulating, horizontally extending flows of circulating freezing air are hereby brought about in the freezer, which subsequently pass through the conveyor chain system supporting the items to be frozen at two different levels of height. With this system, however, in order to hold the trays in place horizontally, use is made of two parallel extending support chains connected to the trays in each their end areas of the individual trays, and the purpose of providing two circulating flows of freezing air is to direct the upper flow with greater air speed than the lower flow. The object herewith is to reduce dehydration and loss of weight of the items as a consequence of pressure difference internally and externally in relation to the freezer, in that the items are thus led into the freezer and out of it again at the bottom of the freezer. Such a plant, however, is best suited only for hardening of the ice, i.e. cooling, especially edible ice products, from a few degrees of frost to a lower deep-freezing storage temperature. On the other hand, the plant displays problems with the air speed, which is too great for the plant to be able to freeze effectively, so that at the same time material losses from the items lying on the trays in more or less open moulds are avoided during the freezing operation, i.e. freezing from a temperature above zero degrees to below freezing point.
Another known plant of the kind disclosed by way of introduction is described in U.S. Patent publication No. 4,023,376. Here, it is the frame placed in the centre of the freezer which supports the tray conveyor, and which as a whole is arranged with cylindrical configuration with a vertical cylinder axis with the frame as a whole being able to, rotate around this axis. On the outside of the frame cylinder there are arranged quite complicated mechanical guiding elements, so that with a plurality of spiral windings the conveyor trays can be conveyed only one way spirally upwards outside, up and around the cylinder. The advantage of this known plant is that the freezer can be configured with the walls of the freezer lying relatively close to the frame cylinder, in that the freezing aggregate and associated fan or blower is disposed in a stationary manner, i.e. without rotation together with the frame cylinder inside the frame cylinder. The circulation of freezing-air is arranged in such a manner that the freezing aggregate and fan or blower are arranged as a unit which leads the flow of air diametrically in relation to and transversely through the frame cylinder, i.e. with a flow plane formed horizontally. Externally in relation to the frame cylinder, the air flow is divided into two branch flows on each side, each of which flows its own way halfway around the outside of the cylinder and into the freezing aggregate for renewed passage through the aggregate. This construction is mechanically recourse-demanding and, moreover, it is so complicated that as a whole it is difficult to clean and troublesome and time-consuming to maintain and service. However, an advantage of this construction is that the air-flow path is shorter than in the first-mentioned construction, and for this reason the air speed can be kept relatively lower, and the loss of energy involved in the freezing is correspondingly lower.
It is the object of the present invention to provide a plant of the kind disclosed in the introduction which is compact and which displays even better freezing conditions, and where the transport arrangement is able to be configured in a considerably less complicated manner, and such that cleaning and maintenance can be effected much more easily.
According to the invention, this is achieved with a plant of the kind disclosed in the introduction, in that at least two frames for the tray conveyor are arranged at the side of each other, each with its inner area and with the tray conveyor, which is supported by the individual frames, being led substantially externally in relation to the inner area of the individual frames, and where there is passage for the flow of freezing-air in the individual frames between the inner and outer area of the frames, and where in at least one of the inner areas of the frames there is arranged at least one cooling aggregate, and where in at least one of the inner areas of the frames there is arranged at least one fan or blower to direct the flow of freezing air passing through the least one cooling aggregate through the conveyor area with items to be frozen lying in at least two of the frames.
According to the invention, the breadth of the frames is of advantage in achieving the shorter path for the flow of freezing air, in that the breadth direction is substantially coincidental with the direction of the passage of the air flow over the items, and is less than the longitudinal extent of the frames, in that the longitudinal extent is oriented substantially in the plane of the air flow circulation.
In this case, for achieving further short paths for the flow of freezing air, according to the invention it is advantageous if the frames are arranged reasonably closely at the side of each other in the breadth direction of the frames.
In all cases, according to the invention it is with advantage possible to achieve lower air flow speed at the same freezing intensity, and also namely low maximal air flow speed over the items, providing that more than one air flow circulation path is correspondingly arranged in the height direction of the frames, in that in each air flow circulation path there is arranged at least one cooling aggregate, correspondingly with at least one fan or blower for driving the individual circulating air flow.
Embodiments according to the invention, as will also appear in the following where embodiments according to the invention are described in more detail, will be able to be provided with quite compact configuration, but still with sufficient space in and around the freezer for far easier access to be gained to the individual construction elements with regard to the carrying out of maintenance work and cleaning operations.
It should thus also be noted that the level of the maximum air speed across the items in the plant is closer to the average air flow speed for the same freezing intensity, in that the plant does not comprise any really narrow passage-ways, and especially not over the items to be frozen. This means that the risk of outer material being blown off the items is reduced to a considerable degree.